By molecular design, a new ion surface-imprinting technique was set up based on surface-initiated graft-polymerization, and arsenate anion surface-imprinted material with high performance was prepared for the first time. A redox initiating system was constituted by the amino groups on the surface-modified silica gel particles and the ammonium persulphate in the solution. The cationic monomer 2-methacryloyloxyethyl-trimethyl ammonium chloride (DMC) was used as functional monomer and N,N′-methylenebisacrylamide (MBA) was used as cross-linker. In the solution, the monomer molecules were arranged around the template ion, arsenate anion, via ion exchange action, and then the arsenate anion surface-imprinting was carried out along with the surface-initiated graft-polymerization of DMC and MBA, forming arsenate anion surface-imprinted material IIP-PDMC/SiO2. The experimental results show IIP-PDMC/SiO2 possesses specific recognition selectivity and excellent binding affinity for arsenate anion. The selectivity coefficients of IIP-PDMC/SiO2 for arsenate anion are 8.814 and 7.898 relative to chromate and nitrate ions, respectively.
The normal and surface-enhanced Raman scattering of EC are studied by using the M06-2X functional. Different contributions to Raman enhancements of EC adsorbed on Ag 20 cluster are analyzed in detail to explore the enhancement mechanism. The adsorption of EC on Ag 20 cluster involves the static chemical enhancement with enhancements factor (EF) of 10 by forming a new EC-Ag 20 complex. The charge-transfer enhancement with EF of 10 4 is found when a 352nm wavelength, corresponding to the absorption maximum of EC-Ag 20 complex, is taken as an incident light. The electromagnetic enhancement EF of 3.6×10 6 due to the localized surface plasmon resonance (LSPR) of Ag nanosphere at the same excitation wavelength are acquired by the discrete dipole approximation (DDA) method. The combined effect of the chemical and electromagnetic enhancement results in the total relative enhancements factor up to 3.6×10 10. The enhancement mechanisms are successfully explained by the combination of ab initio calculation and discrete dipole appropriation method.
The molecularly imprinted polymers (MIPs) synthesized by conventional bulky imprinting methods suffer from several limitations, such as time-consuming preparation process, poor site accessibility to the target molecules and the lower binding capacity for the target molecules. To overcome these problems in bulking imprinting, in this work, a novel surface-ion imprinting method that not only is simple but also highly effective, is put forward and found. The coupling agent γ-aminopropyltrimethoxysilane (AMPS) was bond onto the surface of silica gel particles, and amino groups were introduced onto the surfaces of silica gel particles, obtaining the modified particles AMPS-SiO 2 . In aqueous solution, the molecules of the cationic monomer methacryloxyethyltrimethyl ammonium chloride (DMC) were first combined around the template ion, phosphate ion, by right of ion exchange action. A redox initiating system was constructed by the amino groups on AMPS-SiO 2 and ammonium persulphate in the solution, and free radicals were produced on the surfaces of silica gel particles. These free radicals initiated the monomer DMC and the crosslinker N,N'-methylene bisacrylamide (MBA) to be graft-copolymerized and crosslinked, and the surface-imprinting of phosphate ion was realized. 3 结论 基于 "离子交换" 和 "表面引发接枝聚合" , 以 实验部分 考察阳离子单体在氨基化硅胶表面引发接枝聚合 的可行性一般来说, 阳离子单体的聚合活性较低, 为了考证 本研究所提出的基于"表面引发接枝聚合"使用阳离子 单体实施模板阴离子在硅胶表面印迹的可行性, 即为了 证实所制得的印迹聚合物层是化学接枝在硅胶表面, 而 不是物理包覆, 参照文献 [28] , 我们首先进行了阳离子单 体 DMC 在氨基化硅胶表面引发接枝聚合实验: (1)用偶 联剂 γ-氨丙基三甲氧基硅烷(AMPS)对硅胶微粒进行表 面改性, 即将 KH-540 化学键合于硅胶表面, 制得了 KH-540 键合量为 1.50 mmol/g(采用热失重和酸碱滴定 两种方法测得)的改性硅胶微粒 AMPS-SiO 2 ; (2)在装有 电动搅拌器、回流冷凝管的四口烧瓶中加入 1.0 g 的改 性微粒 AMPS-SiO 2 , 再加入 100 mL 蒸馏水和 8 mL 单体 DMC, 通氮气 30 min, 排除反应体系中的空气, 然后将 体系温度升至 35 , ℃ 用少量蒸馏水溶解 0.0866 g 引发 化 学 学 报
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